Luzonite and associated Cu-excess tennantite from the Levant Sn-Cu deposit, Cornwall, England: Evidence for a high sulphidation hydrothermal event

Luzonite, partially replaced by tennantite, was identified in dump specimens from the historic Levant Mine, west Cornwall, in a paragenetic sequence comprising early cassiterite-quartz-pyrite-arsenopyrite overprinted by Cu-Fe sulphides and followed by luzonite and tennantite. Mineral chemical data indicates the luzonite is near-end member and the tennantite is so-called Cu-excess tennantite, the implication being its Fe content (2.01-4.04 at.-%) is present entirely as Fe3+ in the sulphide lattice. Both the luzonite and its replacement product, Cu-excess tennantite, indicate that at least one hydrothermal episode in the long-lived Levant mineralising system involved influx of oxidised, high-intermediate sulphidation fluids. The presence of fine bornite and covellite lamellae in Cu-excess tennantite are interpreted to be post-depositional exsolution products. The luzonite has a sulphur isotope delta S-34 of 0 +/- 0.3 parts per thousand and it is tentatively proposed that the luzonite-tennantite depositing event represented a pulse of essentially pure magmatic-hydrothermal fluid.